Once your account is activated, you can login to the control panel and click on the "Billing Statement" icon.
It will present you with a list of bills (normally just two items on a new account). Click on the first one at the bottom to view the statement. To print it, click on the printer icon in the header of the table.
By default your subsequent invoices will also be emailed to you.
For more information see: Billing and Payment in the control panel user's guide.